What distinguishes the great songs from the good songs?

For a Gospel song to be considered “good,” its melody must be singable and memorable, and its lyrics must be coherent, Biblical, and generally well-crafted all around. This is a reasonably quantifiable threshold. 

It’s a little harder to tell what sets the great songs apart. Any number of factors contribute, of course. These would include a particularly well-crafted lyric, a particularly fresh main idea/hook, a particularly memorable or singable melody, and the absence of weak rhymes, unclear lyrics, a few too many lines you’ve heard dozens of times before, bad doctrine, and monotonous melodies. Of all these factors, which is the most important?
What is the most important thing that sets the great songs apart from the ones that are merely very good?
Culled from http://www.southerngospelblog.com/archives/19664